Russian engineers might have sabotaged jets sent to Ukraine, according to Slovak Defense Minister Jaroslav Nad.

According to the Kyiv Independent, Nad recently said that Russian engineers were at an air base where several Slovak MiG-29 fighter jets were located. The jets were eventually supplied to Ukraine amid their ongoing war with Russia, which began on February 24, 2022.

According to the Slovak newspaper Dennikn, Slovak Air Force General Ľubomír Svoboda said that the Russian engineers were at the air base because they had more knowledge of the MiG-29 jets and helped to repair them.

“They were able to fly, but that doesn’t mean they were also capable of combat,” Nad said, according to the Kyiv Independent. “The defects appeared only in those parts accessed by Russians.”

Nad’s comments came shortly after Slovakia announced that it was planning to send several MiG-29 jets to Ukraine to help in the war against Russia.

“The first four MiG-29 fighter jets were safely handed over to the Ukrainian Armed Forces and have already left the territory of the Slovak Republic,” Nad wrote in a Facebook post on March 23. “This Government will continue to help save innocent human lives, whoever, for any reason, or otherwise, is thrown on the ground.

“We are doing the right thing because it is Russia that invaded Ukraine, it is Russia that is in Ukraine and it is Russia that when it withdraws troops the war will end immediately…In the following weeks, the remaining aircraft will be handed over to Ukraine, however, for operational reasons we will not provide any further information in advance.”

Prior to the announcement by Slovakia, Polish President Andrzej Duda announced that his country was sending MiG-29 jets to Ukraine.

“Firstly, literally within the next few days, we will hand over, as far as I remember, four aircraft to Ukraine in full working order,” Duda said last month. “The rest are being prepared, serviced.”

Since the beginning of the war in Ukraine, which began with the Russian invasion, several North Atlantic Treaty Organization (NATO) nations, such as Slovakia and Poland, have supplied Ukraine with military assistance packages. Ukrainian President Volodymyr Zelensky has repeatedly asked Western nations for additional aid.

A group of U.S. senators recently sent a letter to Defense Secretary Lloyd Austin, urging the U.S. to send F-16 fighter jets to Ukraine.

“After speaking with U.S., Ukrainian, and foreign leaders working to support Ukraine at the Munich Security Conference last month, we believe the U.S. needs to take a hard look at providing F-16 aircraft to Ukraine,” the letter, which was obtained by Politico, said.

However, President Joe Biden has said that he doesn’t have any plans at this point to send the fighter jets to Ukraine.